Middledown and Rightdown?

[Andrew Newell Mickish <am2q+@andrew.cmu.edu>]

Is there a standard way to generate middledown and rightdown mouse events
from a mouse with only one button?  It would not be appropriate to use
one of the "real" modifier keys on a mouse click, because then you couldn't
talk about control-rightdown, for example.

I was thinking of checking to see if the M or R keys are pressed during a
mouse click, to indicate middle and rightdown events.  Is there a way to
check whether a particular key is being pressed?  I found the function
GetKeys in Inside Macintosh, but it always returns NIL for me (I think it
is supposed to return a keymap record).  How do I use this function, or
should I be trying something different?

Thanks,

--Andrew MIckish